Late Blight-resistant Tomato Varieties Evaluation in Florida

In Florida, late blight (LB) caused by Phytophthora infestans (P. infestans), is a destructive disesase responsible for entire crop losses in the Solanaceae family such as tomato and potato. P. infestans causes large-scale and widespread damages to winter tomato production because of the ideal climatic conditions for the disease development.  Tomato varieties resistant to P. infestans are available in the market; however, evaluation of resistance levels of these varieties has not been performed in Florida. Therefore, the objective of this study was to evaluate resistant tomato varieties to P. infestans on disease resistance, yield, and fruit postharvest quality.  The study was conducted in the UF/IFAS Southwest Florida Research and Education Center in Immokalee, FL during spring 2014. Tomato varieties round (FL 47, Defiant PhR, Mountain Merit, and Iron Lady) roma-type (Plum Regal), campary (Mountain Magic), cherry (Jasper) and mini-roma (Juliet) were transplanted on 2 Jan 2014 into polyethylene mulch fumigated beds. Data collection consisted of LB disease severity (%), marketable and unmarketable fruit yield, and postharvest quality.  Highly susceptible varieties with no resistance genes, FL 47 and Juliet, had 95 and 87%, respectively, of the foliage with LB symptoms. Moderately susceptible Plum Regal was significantly higher than varieties containing both resistance genes but still was greatly reduced in disease severity compared to the susceptible varieties. Tomato varieties containing both Ph2 and Ph3, Defiant, Mountain Merit, Iron Lady, Mountain Magic, and Jasper had less than 10% of symptomatic foliage. Total season marketable and unmarketable yields were not different among LB-resistant varieties (1,102 to1,369 boxes/acre) and higher than ‘FL 47’. ‘Mountain Merit’ had higher extra-large fruit yield than the other varieties evaluated. The roma-type tomato ‘Plum Regal’ produced 1,492 boxes/acre total season marketable yield of which 40% was large fruit category. The cherry tomato ‘Jasper’ produced a total season marketable yields of 134.4 tons/acre with an average fruit size of 5.8 g. However, mini-roma LB-susceptible ‘Juliet’ produced only 2.7 tons/acre total season marketable yields of with an average fruit size of 22.7 g. Campary tomato ‘Mountain Magic’, total season marketable yields was 12.7 tons/acre of which 54% was medium fruit size. Among the round tomato varieties, Defiant PhR and Mountain Merit had higher TSS and pH than Iron Lady. Fruit color was higher for ‘Defiant PhR than for ‘Iron Lady’. Tomato varieties containing both Ph2 and Ph3 had less than 10% LB symptomatic foliage and produced higher marketable yields than susceptible varieties.